Circuit for preventing breakdown of a load resulting from wrong connection of a power source

Abstract

In a circuit for preventing breakdown of a load resulting from a wrong connection of a power source, there are provided a first load to which a DC voltage source should be applied at a predetermined polarity and to which a wrong polarity connection of the DC voltage source should be prevented, a second load to which the DC voltage should be applied, and a transistor having the base thereof connected to the second load and the collector thereof connected to one terminal for connection with the DC voltage source. The first load is connected between the base electrode and emitter electrode of the transistor. The junction of the first and second loads is connected to another terminal for connection to the DC voltage source.

What is claimed is: 
     
       1. A circuit for preventing breakdown of a load resulting from a wrong connection of a power source, comprising: a first load to which a DC voltage source should be applied at a predetermined polarity and to which a reverse-polarity connection of the DC voltage source should be prevented, wherein the DC voltage applied to the first load is a regulated voltage;   a second load the output of which controls said first load, wherein the DC voltage applied to the second load is not required to be regulated;   a transistor having the base electrode thereof connected to one side of said second load, one electrode of said transistor other than said base electrode being connected to one terminal for connection with said DC voltage source, said first load being connected between the other side of said second load and the other transistor electrode, wherein said other electrode has a lower reverse-withstanding voltage than the reverse-withstanding voltage of the junction between said base electrode and said one electrode, wherein said first and second loads are set to permit a current flow which operates said transistor in its saturation range; and   means for connecting said other side of said second load to another terminal for connection to said DC voltage source.   
     
     
       2. A circuit according to claim 1, wherein said transistor is a PNP transistor, said one electrode is the collector electrode and said other electrode is the emitter electrode. 
     
     
       3. A circuit according to claim 1, wherein the DC voltage to be applied to said first load is higher than that to be applied to said second load. 
     
     
       4. A circuit according to claim 1, wherein said first load includes logic circuitry and wherein said second load is an oscillator circuit. 
     
     
       5. A circuit according to claim 4, further comprising voltage regulating means, wherein said DC voltage source is coupled to said transistor and loads through said regulating means. 
     
     
       6. A circuit according to claim 4, further comprising electro-acoustic conversion means coupled to the oscillating output of said oscillator circuit. 
     
     
       7. A circuit according to claim 4, further comprising means for determining whether the voltage of a circuit under test is a logical "0" or "1" for producing respective output signals corresponding thereto, and means for applying said determining means output signals to said logic circuitry.